Publications

The Penyu Basin is composed of several discrete NE-SW trending Tertiary half grabens separated by intervening basement highs within the Sunda Microplate. Rifting occurred from Middle Eocene to Early Oligocene and was a critical control on the deposition of syn-rift Benua/Lama and Belut Formations in the Cherating Graben and Jemaja Basins. Post-rift deposition of Upper Oligocene Gabus/Udang Formations provided the main reservoir/seal units. Mid-Late Miocene inversion on the graben-bounding faults created a series of ENE-WSW trending anticlines which have proved to be successful traps in the Malay and West Natuna Basins. Wells drilled up to now that tested this play in the Penyu Basin have been largely unsuccessful due to lack of access to a present day hydrocarbon generating kitchen. The Janglau-1 well successfully tested a new syn-rift play in Cherating Graben. Distal alluvial fan deposis of the Belut Formation provided a sequence of stacked reservoir/seal pairs interbedded with oil-prone lacustrine source rocks. Multiple zones of over-pressured oil pay confirm the presence of an active oil-generating kitchen at the present day. Recent basin modeling showed that each sub-basin has an independent kitchen with different sediment thickness, source rock formation, organic richness and maturity. Geochemistry data from the Jemaja Basins indicate the Lower Gabus and Belut Formations are prolific source rocks in the basin. A Belut source rock interval in the Jemaja East sub-basin has medium to very high organic content and is a mixture between gas and oil prone kerogen. It has reached maturity in the depocentre of the basin and has generated significant amounts of oil and gas since 15Ma. Modeling indicates basement focused migration would charge stratigraphic and basement-drapes traps in the Jemaja High on the northern flank of the sub-basin. Recent interpretation on 3D surveys in the Gurita Block (which covers the eastern part of the Penyu Basin) has highlighted attractive prospects in both syn-rift and post-rift sequences on the Jemaja High and Cherating Graben and has redefined the Penyu Basin as an attractive exploration province.